Fig. 1. Schematic diagrams of multi-layer films (left) and rolled-up quantum well infrared device (right). The blue curve is the neutral line which is the boundary between tensile stress (green arrows) and compressive stress (red arrows) in the right diagram. The SEM image (top view) of rolled-up quantum well nanomembrane is in the top right inset

Fig. 2. (a) PL spectra of rolled-up nanomembranes with different diameters, (b)~(f) are the fitting curves of PL spectra. “Cumulative Curve” is abbreviated as “C. Curve”

Fig. 3. (a) Interband transition peak changes with the diameter of rolled-up nanomembrane; (b) Intraband transition peaks (conduction band ∆e, Valence band ∆hh) change with the diameter of rolled-up nanomembrane; (c) The movement of conduction band under tensile stress. After rolling, both of energy levels (e₀ and e₁) move up and e₀ moves more; (d) The red dotted line is the neutral line. Part I: The neutral line is at the outermost at the beginning of rolling. Part II: The neutral line moves to the outside of QW₁. Part III: The neutral line moves between QW₁ and QW₂. Black arrows indicate the stress in QW₁ and red arrows indicate the stress in QW₂. The blue arrows indicate the resultant stresses in the two quantum wells. “Comululative Stress” is abbreviated as “C. Stress”

Fig. 4. Photocurrent spectra of infrared detectors for flat and rolled-up (diameter: 62 μm) nanomembranes under 400 mV applied voltage, collected at 40 and 70 K separately

Fig. 5. (a) Optical microscopy image of wrinkled nanomembrane (top view). The peaks of raised parts are marked with “I”, “II”, “III” and“IV”. Figure (b) is the section view of the red dotted line in the top right corner of Figure (a). A, C points are the peaks and B point is the valley. “1”, “2” points are between A and B points. The values (unit: eV) in the brackets are the peaks of their PL spectra, where the peak positions are the same for “1” and “2” points, (c) Comparison of blackbody responsivity between rolled-up nanomembrane detector (diameter: 150 μm) and the wrinkled nanomembrane detector, (d) The red line is neutral line and the quantum wells in the dotted neutral line regions are both compressive. For the quantum wells in middle solid neutral line region, one quantum well is compressive, and the other is in tensile stress